Control system for machine tool



Oct. 11, 1966 E. c. JOHNSON ETAL 3,273,317

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AT ORNEY E. c. JOHNSON ETAL 3,278,817

' CONTROL SYSTEM FOR MACHINE TOOL Oct. 11, 1966 18 Sheets-Sheet 5 Original Filed Aug. 1, 1955 Amy F E E I L t L E 5 QTM m E C E E E I E I CC C F lmi i ONM N m NOM mom 00m 1 INVENTORS E. CALVIN JOHNSON AVREL MASON BY CHARLES A. PIPER CH|EN"B SUNG 62X ATT NEY Oct. 11; 1966 E. c. JOHNSON ETAL 3,

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CONTROL SYSTEM FOR MACHINE TOOL Ongmal Flled 1, .1955 528 18 Sheets-Sheet 12 INVENTORS E. CALVIN JOHNSON AVREL MASON BY CHARLES A. PIPER CHIEN-BOR suns TORNEY Oct. 11, 1966 E; c. JOHNSON ETAL 3, 7

CONTROL SYSTEM FOR MACHINE TOOL Original Filed Aug. 1, 1955 l8 Sheets-Sheet 15 INVENTORS E. CALVIN JOHNSON AVREL MASON BY CHARLES A. PIPER CHIEN- OR SUNG A ORNEY Oct. 11, 1966 E. c. JOHNSON ETAL 3,278,817

CONTROL SYSTEM FOR MACHINE TOOL 18 Sheets-Sheet 14 Original Filed Aug. 1, .1955

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Oct. 11, 1966 E. c. JOHNSON ETAL 3,278,817

CONTROL SYSTEM FOR MACHINE TOOL Original Filed Aug. 1, 1955 18 Sheets-Sheet 15 I I5IO I5l6 g l524 IIIIII I 7 w 5 6 III I7 I I7] 5 5 0 n I7I|| IIISI III 5 I 7 IIIIMIIIIII 5 5 6 l I I6 II IIIII 5 II II II| .I I I I I G H H U 2) 8 6S M 3 ma 5 m w Lw I L AP M N A N N N N I I I I MC M M M R0 R R R E E E E m T T T TERMINAL I5IO I l TIME F/G- l9 A ORNEY Oct 1955 E. c. JOHNSON ETAL 3,

CONTROL SYSTEM FOR MACHINE TOOL l8 Sheets-Sheet 16 0- I6IO Original Filed Aug. 1, 1955 ases (CLOCK PULSES) (L) TERMINAL I626 (SPINDLE PULSESI 3 o I I I7 II III I I m 6 I I mw W m 0 m 6 6 z a N T 2 W 2 I U M P E P E R T T T T E UA UA T 06 0G TERMINAL I606 TIME IN V EN TORS ALVIN JOHNSON EL MAS LES A N-B AVR ON CHAR PIPER CHIE OR SUNG flzaI 7 A ORNEY Oct. 11, 1966 E. c. JOHNSON ETAL 3,273,317

CONTROL SYSTEM FOR MACHINE TOOL Original Filed Aug. 1, 1955 18 Sheets-Sheet 1'7 FJJW ww QI T Aw ZOCLmOm m EzEw 2d CL mun: Eniiz .PDmhDO hum- ONO FFJDS Paar-.30 hummmm 5m 20040 $23 mmwwzt. FDmkDO PmuJ O02 mumm -mp. .PDmhDO baud 20- mmwmzmh FDA-E hum O00- mmw mh P315 humJ INVENTORS E. CALVIN JOHNSON AVREL MASON BY CHARLES A. PIPER CHlEN-BOR SUNG and 7 A ORNEY United States Patent Ofiice 3,278,817 Patented Oct. 11, 1966 1955. This application July 31, 1958, Ser. No. 752,686

- 24 Claims. (Cl. 318-18) This application is a continuation of co-pending application Ser. No. 525,524, filed Aug. 1, 1955 by Ewell Calvin Johnson, Avrel Mason, Charles A. Piper and Chien- Bor Sung, and now abandoned.

This invention relates to a machine tool and more particularly to an automatically controlled machine tool.

At present a considerable amount of time and expense is involved in producing cams having close tolerance requirements. The main reason for this is that most of the work on such cams must be done by hand. For example, it may require up to four months for a skilled workman to make a single high precision cam having a three dimensional configuration.

This invention provides a machine tool which operates automatically to cut cams in accordance with the dictates 'of recorded information fed to the machine. The machine includes a spindle for rotating a workpiece and a tool movable in an axial and radial direction relative to the workpiece. The tool movement in the axial and radial directions is synchronized with the spindle rotation to cut a three dimensional cam having the desired contour.

The movement of the tool in the axial direction is controlled by the spindle because of a geared relationship and .the movement of the tool in the radial direction is controlled in accordance with recorded information in numerical form which is fed to the machine tool. This information is utilized to provide a particular number of electrical pulses representative of the numerical information for driving the tool in the radial direction a distance proportional to the number of electrical pulses.

From recorded information, such as may be provided on a tape, the machine tool can cut high precision cams in relatively short periods of time. For example, it has been found that most cams can be cut in less than four hours.

An object of this invention is to provide an automatically controlled machine tool.

Another object of this invention is to provide a machine tool for receiving recorded information and for utilizing the information to control the operation of the machine.

A further object of this invention is to provide a machine tool of the above character for utilizing recorded information in numerical form.

Still another object is to provide a machine tool of the above character for producing a number of electrical pulses representative of the numerical information.

A still further object of this invention is to provide a machine tool of the above character for producing a movement of a part of the machine a distance proportional to the number of electrical pulses produced.

Another object of this invention is to provide a machine tool of the above character having a spindle for rotating a workpiece and a tool movable relative to the workpiece for cutting a cam.

A further object is to provide a machine tool of the above character for synchronizing the movement to the tool with the spindle rotation so as to out three dimensional cams.

Other objects and advantages will become apparent 'ages at diiferent terminals of the multivibrator in FIG- ,URE 18.

from the following detailed description and from the appended drawings and claims.

In the drawings:

FIGURE 1 is a simplified block diagram of a machine tool representing an embodiment of this invention.

FIGURE 2 shows the electronic components that may be included in certain blocks in FIGURE 1.

FIGURE 3 shows the relationship between different voltages at strategic points in FIGURE 2.

FIGURE 4 is an end view of a cam blank illustrating a movement of a tool in a radial direction relative to the cam blank.

FIGURE 5 illustrates the tool movement between certain points on the cam blank in FIGURE 4.

FIGURE 6 is a side view of the cam blank in FIGURE 4 illustrating a movement of the tool in an axial direction relative to the cam blank.

FIGURE 7 is a block diagram of a machine tool constituting one embodiment of this invention.

FIGURE 8 shows a tape handling system for feeding tape to the tape reader in FIGURE. 7.

FIGURE 9 is an enlarged view of sections of the tape shown in FIGURE 8.

FIGURES 10 to 17, inclusive, show in detail the electronic components that may be included in certain blocks in FIGURE .7.

in a particular type multivibrator used in the machine tool.

FIGURE 19 shows the relationship between the volt- FIIGUR E 20 shows the circuitry that may be included 'in another type of multivibrator used in the machine tool.

, FIGURE.21 shows the relationship between the volt FIGURES 22 and 23 show the relationship between the voltages at strategic terminals in FIGURE 13 under two different conditions of machine operation.

FIGURE 24 is a side view of a cam blank illustrating paths of movement which may be followed by a tool to cut a three dimensional cam.

To facilitate the understanding of this invention it will first be explained in connection with the simplified block diagram in FIGURE 1.

A tape reader has its output connected to a temporary storage register 102 which in turn has its output connected to an active storage register 104. The active storage register 104 has an output connected to an interpolator 108. The interpolator 108 has an output connected to an error register 110 and also has an output which is connected to the tape reader 100, the temporary storage register 102 and the active storage register 104. The interpolator 108 introduces a particular number of electrical pulses to the error register in accordance with information fed to the tape reader 100, as will be hereinafter described.

A spindle control 106 and the error register 110 have their outputs connected to servo amplifiers 112 and 114, respectively. The output of the amplifier 112 is introduced to a spindle drive 116. The drive 116 may include the combination of .a torque motor, a valve and a hydraulic motor, known to persons skilled in the art. The voltage output of the servo amplifier 112 is introduced to the torque motor to produce a displacement of the motor a distance proportional to the magnitude of the voltage and in a direction determined by the polarity of the voltage. This controls the opening of the valve for introducing fluid under pressure to the hydraulic motor for driving the motor at a speed and in a direction dependent upon the magnitude and polarity of the voltage output from th servo amplifier.

The drive 116 operates to rotate a shaft 118 journalled in a frame 120. The shaft 118 is provided with a pair of bevel gears 122 and 124 and a gear 126. During a rotation of the shaft 118, the gear 122 drives a bevel gear 128 which rotates a spindle 130 and a workpiece, such as a cylindrical cam blank 132, mounted on the spindle. A tail stock 134 supports the cam blank 132 at its opposite end.

During the rotation of the shaft 118 the gear 124 drives a bevel gear 136 for rotating a lead screw 138 which is screwed into a carriage 140. The rotation of the screw will produce a movement of the carriage relative to the frame 120 and in the directions indicated by the arrows at 142. This movement is in an axial direction relative to the cam blank 132.

The rotation of the shaft 118 also causes the gear 126 to drive a gear 144 which rotates a shaft 146 and a spindle reading head 148 on the shaft. The reading head 148 may be a magnetic reading head which is adapted to produce at its output a particular number of electrical pulses at uniform intervals during each revolution of the reading head 148. Magnetic reading heads are commercially available and their operation is known to persons skilled in the art. For example, Telecomputing Company of California makes a magnetic reading head Model No. 15A which may be conveniently used to produce electrical pulses.

Since the reading head 148and the spindle 130 are driven from the same shaft 118, the reading head produces a particular number of pulses at uniform intervals for each revolution of the spindle. For example, the gear ratios may be such as to produce an output of 576 pulses during each revolution of the spindle 130 or an output of 16 pulses for each angular movement of the spindle. These pulses, which will hereafter be re ferred to as spindle pulses, are introduced to the interpolator 108.

The output of the servo amplifier 114 is introduced to a cross feed drive 150 mounted on the carriage 140. The drive 150 may be similar to the drive 116 and operates to rotate a lead screw 152 which is screwed into a tool carriage 154. The rotation of the screw 152 will produce a movement of the tool carriage 154 relative to the carriage 140 and in the directions indicated by the arrows at 156. This movement is in a radial direction relative to the cam blank 132 and may be referred to as a cross feed movement relative to the cam blank. The cross feed movement is substantially perpendicular to the axial movement previously described. A tool holder 158 is mounted on the carriage 154 and a milling cutter or tool 160 is supported in the holder. A cutter drive 162 is adapted to rotate the cutter 160 at a high speed, such as 3600 revolutions per minute.

Since the tool carriage 154 is mounted for movement with the carriage 140, in the axial direction, the carriage 154 and, therefore, the tool 160 can simultaneously move in an axial and radial direction relative to the cam blank 132 upon rotation of the lead screws 138 and 152. The distance moved in each direction is dependent upon the pitch of the screws 138 and 152. For example, the pitch of the screw 138 may be such as to produce a .005 inch movement of the tool 160 in the axial direction for each revolution of the spindle 130 and the pitch of the screw 152 may be such as to produce a .02 inch movement of the tool in the radial direction for each revolution of the screw.

When the shaft 118 rotates in a clockwise direction as indicated in FIGURE 1, the tool 160 moves axially to the right. The tool 160 moves axially to the left when the shaft 118 is rotated in the opposite direction. Similarly, the tool moves radially towards the axis of the cam blank when the screw 152 rotates in a clockwise direction as shown in FIGURE 1 and the tool moves radially away from the axis of the cam blank when the screw rotates in the opposite direction.

A gear 164 on the screw 152 drives a gear 166 for rotating a shaft 168 which is journalled in a bearing support 170 mounted on the carriage 140. The shaft 168 rotates a cross feed reading head 172 on the shaft. The reading head 172 may be similar to the reading head 148 and produces a particular number of electrical pulses at uniform intervals for each revolution of the screw 152. Since the carriage 154 drives the tool in the radial direction a distance proportional to the number of revolutions of the screw 152, the number of pulses produced by the reading head is proportional to the radial distance traveled by the tool 160. These pulses, which will hereafter be referred to as feedback pulses, are introduced to the error register 110.

As previously disclosed, the interpolator 108 introduces a particular number of electrical pulses to the error register 110 in accordance with information fed to the tape reader 100. This will be explained in connection with FIGURE 2 which shows electronic components that may be included in the temporary register 102, the active register 104 and the interpolator 108.

In FIGURE 2, the tape reader has an output connected to the left input of a two input bistable multivibrator 202.

Initially, the multivibrator 202 is operating with its left output low and its right output high and the left and right inputs are low. The terms high and low will be used throughout this description to indicate the voltage level at particular terminals as in common binary network analysis. For example, in the network of FIG- URE 2 low may represent 9 volts and high may represent +15 volts.

When the left input of the multivibrator 202 becomes high, the left output changes from low to high and the right output changes from high to low. The multivibrator will remain in this condition until the right input becomes high. When the right input becomes high, the multivibrator returns to its initial condition with the left output low and the right output high. The multivibrator will remain in this condition until the left input becomes high again.

Each multivibrator hereinafter described will be a two input bistable multivibrator if in the drawings it is shown to have the same configuration as the multivibrator 202 with inputs in the lower left and right sides of a block and with outputs in the upper left and right sides of the block. Certain inputs or outputs may not be shown if they are not utilized in the network. For example, the right output of multivibrator 202 is not shown since it is not utilized.

The tape reader 100 also has outputs connected to the left inputs of bistable multivibrators 204, 206 and 208. The left outputs of the multivibrators 202, 204, 206 and 208 are connected to inputs of diode and gates 210, 212, 214 and 216, respectively. An and gate in computer terminology is a gate which has a high output only when all of the inputs are high. If any of the inputs are low the output of the gate will be low. Each gate hereinafter described will be a diode an gate if it is shown in the drawings as a circle having a dot in its center.

The multivibrators 202, 204, 206 and 208 and the gates 210, 212, 214 and 216 are components which may be included in the temporary storage register 102 in FIG- URE 1.

The gates 210, 212, 214 and 216 have their outputs connected to the left inputs of multivibrators 218, 220, 222 and 224, respectively. The multivibrators 18, 220, 222 and 244 are components that may be included in the active storage register 104 in FIGURE 1.

The left outputs of the multivibrators 218, 220, 222 and 224 are connected to inputs of gates 226, 228, 230 and 232, respectively. Electrical pulses such as may be produced by the spindle reading head 148 in FIGURE 1 

1. IN A CONTROL SYSTEM INCLUDING SHAFT MEANS AND FEED MEANS HAVING AN ACTUATOR, PULSE GENERATOR MEANS OPERATED BY ROTATION OF SAID SHAFT MEANS FOR SUPPLYING PULSES IN TIMED RELATIONSHIP TO THE ROTATION OF SAID SHAFT MEANS, SAID FEED ACTUATOR BEING OPERATED BY SAID PULSE GENERATOR MEANS AT A SPEED SYNCHRONIZED WITH THAT OF SAID SHAFT MEANS. 